Microwave ovens have generally been energized with microwave energy from magnetrons which require high voltage power supplies, and since such magnetrons are substantially constant voltage devices requiring several thousand volts, power supplies preferably should deliver power at voltage and current levels which produce operation of such magnetrons in a particular mode substantially independent of a wide range of microwave loads positioned in a cavity and in a region of high efficiency of the magnetron. Such power supplies have generally operated with 60-cycle transformers, with the desired regulation of current being produced by resonating action or with complex regulating structures which vary the magnetic field applied to the magnetron as a function of the space current through the magnetron. Such devices are bulky and heavy. In addition, control of such circuits to regulate or to vary the average microwave power of the oven requires relatively complicated controls.